Ecological environmental effects of Yellow River irrigation revealed by isotope and ion hydrochemistry in the Yinchuan Plain, Northwest China

Water is the most critical resource that affects the stability of ecosystems and socio-economic development in arid and semi-arid regions. The rational development and utilization of water resources in Yinchuan Plain play a vital role in supporting and leading its ecological environment protection and high-quality agricultural development. Irrigation water from the Yellow River and groundwater are the main water resources of Yinchuan Plain. To understand the ecological impact of the Yellow River irrigation, the research analyzed the interaction between surface water and shallow groundwater using isotope hydrochemical method. The results show that both surface water and shallow groundwater are neutral and alkaline, the hydraulic relationships among the water bodies are strong. The correlation between 17O-excess and delta 18O depends on the proportions of precipitation recharge and the intensity of evaporation. The chemical characteristics of water are controlled by evaporation, irrigation activities and water-rock interactions. Hydrochemical characteristics indicate that Yellow River irrigation has little impact on the Yellow River, but it has caused a rise in the groundwater level, intensified evaporation, and aggravated soil salinization. Isotopes indicate that Water-Saving Transformation Project has brought about a new ecological problem-lake shrinkage while reducing salinization. Therefore, we propose to moderately increase the amount of water diversion to flush the groundwater ions and extract the groundwater for human activities during the irrigation period to reduce salinization and water resource shortage. Salinization should be considered in relation to sustainable agricultural development and ecological environment health in Yinchuan Plain as well as other similar arid regions.